A novel tool to determine nucleus density in colored system with NA

A novel tool to determine nucleus density in colored system

with NA

Citation for published version (APA):

Ma, Z., Steenbakkers, R. J. A., Housmans, J. W., Peters, G. W. M., & Meijer, H. E. H. (2009). A novel tool to

determine nucleus density in colored system with NA. Poster session presented at Mate Poster Award 2009 :

14th Annual Poster Contest.

Document status and date:

Published: 01/01/2009

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A novel tool to determine nucleus

density in colored system with NA

Z. Ma, R.J.A. Steenbakkers, J.W. Housmans, G.W.M. Peters, H.E.H. Meijer

Polymer Technology Group, Department of Mechanical Engineering, TU/e

/ department of mechanical engineering

Introduction

Adding nucleating agent (NA) into a crystallizable polymer system is a common way, applied in polymer industry, to control crystallization and tailor mechanical and optical properties of products. These properties are closely related to the resulting nucleus density. For colored NA systems, nucleus density becomes too large and subsequently changes the optical properties, which will both make quantification of nucleus density difficult with optical microscopy. The aim of this project is to develop a new method to determine the nucleus density for colored NA systems with rheometry.

Materials and Experiments

An isotactic polypropylene (Borealis HD120MO, Mw = 365 kg/mol, PDI = 5.4) was compounded with the organic NA (U-Phthalocyanine, bulk density = 310 kg/mol) at a concentration of 0.2 wt%, by which the system was colored blue.

Method

ln(1

)

( )

4

( )

N T

G T t

φ

π

−

−

=

*

*

0

A f

+

B

f

+

C

=

A linear viscoelastic version of the three dimensional generalized self-consistent method (3D GSCM) of Christensen and Lo[1]_{was used. This}

model has been validated by experimental data in our previous work[2]_.

If spherulites are formed, the relative dynamic modulus, f*G=G*/G*0, is obtained from

A Rheometrics ARES rheometer was used with a plate-plate geometry for small-amplitude oscillatory measurements at an angular frequency of 5 rad/s and a strain of 0.5%.

References

[1] R.M. Christensen, K.H. Lo, J.Mech.Phys.Solids (1979) 27:315. [2] R.J.A. Steenbakkers, G.W.M. Peters. Rheol Acta (2008) 47:643.

[3] H.Zuidema, G.W.M. Peters, H.E.H. Meijer, Macromol. Theory Simul. (2001) 10:447. [4] M. Avrami, J. Chem. Phys. (1939) 7:1103; (1940) 8:212; (1941) 9: 177.

Kinetics of space filling at different temperatures depend on both nucleus density and growth rate. Growth rate is a known exponential function of temperature[3]_,

φ

1 0 * G /G

μ =

Fig. 3 Nucleus density formed at different temperatures. Prediction for iPP is from [3].

Conclusion

A suspension-based rheological method to determine the nucleus density is applied to colored NA filled systems, where optical microscopy is not possible. Nucleus densities of this system and pure iPP, crystallizing at various temperatures, determined by this method are shown in Fig. 3.

with G* the effective dynamic modulus and G*0the dynamic modulus of

the continuous phase. The complex coefficients A*, B* and C* depend on space filling , , which is the ratio of the complex moduli of the continuous phase (G*0) and dispersed phase (G*1), and v0 and v1,

being the Poisson ratios of both phases.

where for HD120MO, parameters Gref, cG, TG,ref are 3*10-6 m/s, 2.3*10-3_{and 363 K, respectively. And then, nucleus density could be}

obtained using Avrami equation[4]_:

2 ,

( )

exp

(

)

G T

=

G

⎡

_⎣

−

c T

−

T

⎤

_⎦

(1)

(2)

(3)

Fig. 1 Evolution of G’ with time during crystallization of NA systems at different temperatures.

1)Obtain raw data from rheological measurements.

2) Derive space filling from dynamic moduli.

In this case, space filling is unknown and is obtained from the measured f*G by minimizing eq. (1). Results obtained by fitting are shown in Fig. 2.

Fig. 2 The space filling derived from rheological data.

3) Use space filling to determine nucleus density.